1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 #include <linux/kthread.h>
4 
5 /*
6  * Any file that uses trace points, must include the header.
7  * But only one file, must include the header by defining
8  * CREATE_TRACE_POINTS first.  This will make the C code that
9  * creates the handles for the trace points.
10  */
11 #define CREATE_TRACE_POINTS
12 #include "trace-events-sample.h"
13 
14 static const char *random_strings[] = {
15 	"Mother Goose",
16 	"Snoopy",
17 	"Gandalf",
18 	"Frodo",
19 	"One ring to rule them all"
20 };
21 
22 static void simple_thread_func(int cnt)
23 {
24 	unsigned long bitmask[1] = {0xdeadbeefUL};
25 	int array[6];
26 	int len = cnt % 5;
27 	int i;
28 
29 	set_current_state(TASK_INTERRUPTIBLE);
30 	schedule_timeout(HZ);
31 
32 	for (i = 0; i < len; i++)
33 		array[i] = i + 1;
34 	array[i] = 0;
35 
36 	/* Silly tracepoints */
37 	trace_foo_bar("hello", cnt, array, random_strings[len],
38 		      current->cpus_ptr);
39 
40 	trace_foo_with_template_simple("HELLO", cnt);
41 
42 	trace_foo_bar_with_cond("Some times print", cnt);
43 
44 	trace_foo_with_template_cond("prints other times", cnt);
45 
46 	trace_foo_with_template_print("I have to be different", cnt);
47 
48 	trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask);
49 }
50 
51 static int simple_thread(void *arg)
52 {
53 	int cnt = 0;
54 
55 	while (!kthread_should_stop())
56 		simple_thread_func(cnt++);
57 
58 	return 0;
59 }
60 
61 static struct task_struct *simple_tsk;
62 static struct task_struct *simple_tsk_fn;
63 
64 static void simple_thread_func_fn(int cnt)
65 {
66 	set_current_state(TASK_INTERRUPTIBLE);
67 	schedule_timeout(HZ);
68 
69 	/* More silly tracepoints */
70 	trace_foo_bar_with_fn("Look at me", cnt);
71 	trace_foo_with_template_fn("Look at me too", cnt);
72 }
73 
74 static int simple_thread_fn(void *arg)
75 {
76 	int cnt = 0;
77 
78 	while (!kthread_should_stop())
79 		simple_thread_func_fn(cnt++);
80 
81 	return 0;
82 }
83 
84 static DEFINE_MUTEX(thread_mutex);
85 static int simple_thread_cnt;
86 
87 int foo_bar_reg(void)
88 {
89 	mutex_lock(&thread_mutex);
90 	if (simple_thread_cnt++)
91 		goto out;
92 
93 	pr_info("Starting thread for foo_bar_fn\n");
94 	/*
95 	 * We shouldn't be able to start a trace when the module is
96 	 * unloading (there's other locks to prevent that). But
97 	 * for consistency sake, we still take the thread_mutex.
98 	 */
99 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
100  out:
101 	mutex_unlock(&thread_mutex);
102 	return 0;
103 }
104 
105 void foo_bar_unreg(void)
106 {
107 	mutex_lock(&thread_mutex);
108 	if (--simple_thread_cnt)
109 		goto out;
110 
111 	pr_info("Killing thread for foo_bar_fn\n");
112 	if (simple_tsk_fn)
113 		kthread_stop(simple_tsk_fn);
114 	simple_tsk_fn = NULL;
115  out:
116 	mutex_unlock(&thread_mutex);
117 }
118 
119 static int __init trace_event_init(void)
120 {
121 	simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
122 	if (IS_ERR(simple_tsk))
123 		return -1;
124 
125 	return 0;
126 }
127 
128 static void __exit trace_event_exit(void)
129 {
130 	kthread_stop(simple_tsk);
131 	mutex_lock(&thread_mutex);
132 	if (simple_tsk_fn)
133 		kthread_stop(simple_tsk_fn);
134 	simple_tsk_fn = NULL;
135 	mutex_unlock(&thread_mutex);
136 }
137 
138 module_init(trace_event_init);
139 module_exit(trace_event_exit);
140 
141 MODULE_AUTHOR("Steven Rostedt");
142 MODULE_DESCRIPTION("trace-events-sample");
143 MODULE_LICENSE("GPL");
144